1. Field of the Invention
This invention relates to an automatic transmission for automobiles, and, more particularly, to a parking mechanism of an automatic transmission which ensures reliable parking operation and light releasing operation of a parking range.
2. Description of Related Art
Typically, automatic transmissions for automobiles have, as their transmission means, planetary gear mechanisms or infinitely variable gear mechanisms. Such an automatic transmission is selected and placed into any desired ranges, such as forward ranges, a reverse range, a neutral range and a parking range, by means of a select or shift lever directly operated by a driver. A selection of the parking range causes a parking mechanism to lock a transmission shaft of the automatic transmission. Such a parking mechanism installed in, for instance, an automatic transmission of the type having juxtaposed transmission shafts, includes a parking gear fixedly mounted on one of the transmission shafts, to which a secondary pulley is attached and which is called a secondary transmission shaft, and a parking anchor arm with a pawl. The parking mechanism forces the parking anchor arm to bring the pawl into engagement with the parking gear, by means of which the secondary transmission shaft is mechanically locked. Such a parking mechanism is known from, for instance, Japanese Unexamined Patent Publication No.57-173652.
In automatic transmissions of the type having a long linkage path between the shift lever to the parking anchor arm, various structural elements or parts for the parking mechanism are typically arranged in the linkage path. Consequently, among mass-produced automatic transmissions, parking anchor arms are apt to have variations in stroke or angle of swinging movement due to an accumulation of allowable dimensional errors of these elements. If in fact the parking anchor arm has a large stroke or angle of swinging movement, the parking mechanism provides, on one hand, a reliable operation for a selection of the parking range and, on the other hand, requires a large operational force for releasing the parking range. In contradistinction to this, if the parking anchor arm has a small stroke or angle of swinging movement, the parking anchor arm is subjected to a large reaction force from the parking gear and consequently, accidentally allows the pawl easily disengage from the parking gear. Further, the arrangement of these structural elements in the linkage path requires a large space in an automatic transmission housing, this leads to a bulky configuration of the automatic transmission.